With Mel Gibson’s wife Robyn filing for divorce after twenty eight years, one of the “irreconcilable differences” might be his relationship with raven-haired beauty Oksana. On March 4, Gibson was caught embracing the Russian musician in the waters near his Costa Rican getaway. Another oddity of the trip? Several of his sons, their girlfriends, and other guests were also on hand – with his wife nowhere to be seen.

And while Mel has listed the couple’s date of separation as 2006, sources close to Robyn say it was much later than that. In her papers, Robyn says the date of separation is to be determined. (The later the date, the more money Robyn is potentially entitled to.) But one thing is certain: Mel’s fling with Oksana infuriated Robyn and the next thing you know, divorce papers were filed.

Mel was first publicly spotted with Oksana in Boston last year. Then, in Costa Rica this year, Mel was not shy about displaying his affection for Oksana.

“Mel sort of took hold of her and she came willingly into his arms. They put their arms around each other and kissed pretty passionately for about four or five seconds,” an eyewitness told RadarOnline.com. “The two of them then wandered down the beach and popped in and out of the surf, occasionally touching each other.”

This isn’t the first time Gibson’s fidelity has come under question. Last fall, while he was in Boston shooting the film Edge of Darkness, he was spotted with the stunning lady. She was spotted on the set three days in a row and at least on one occasion emerged from Gibson’s private trailer.

According to papers filed in L.A. County Superior Court, Robyn is looking for joint physical custody of Tom, the couple’s only child who is a minor (they have seven children in total). She is also requesting the actor pay spousal support and attorney’s fees. Though imminent, the couple have not yet formally separated, according to the papers.

The actor-director could be looking at an expensive split, as the couple reportedly made no prenuptial agreement prior to their 1980 marriage. California’s community property laws, in that case, would dictate Robyn would receive half of Mel’s estimated $900 million fortune. Her attorney, Laura Wasser, has experience working on pricey celebrity divorces; Wasser represented Angelina Jolie, Britney Spears and Stevie Wonder in their respective splits.